Uronic acids biosynthesis

Octosyl Acids. Three octosyl uronic acid nucleosides, produced by S. cacaoi sub sp. asoensis are shown in Figure 3. The biosynthesis of (172) and (173) has been reported (1). The replacement of the pyrimidine chromophore of (171) with adenine results in a nucleoside analogue that is a competitive inhibitor of cAMP. 

Uridine, biosynthesis of, 1124 Uronic acid, 994 from aldoses, 994 Urushiols, structure of, 600 UV, see Ultraviolet... 

Fig. 8(a) and (b).—Hypothetical Routes Suggested for the Biosynthesis of Hex-uronic Acid and l-Ascorbic Acid. 

The mechanism whereby the backbone chains of the mucopolysaccharides are elaborated is at present unknown. At least two possible sequences in the biosynthesis could involve stepwise addition of either (1) (alternately) amino sugar and uronic acid or (2) initially formed disaccharide units which may contain a hexuronic or hexosaminic linkage. It is, however, clear that, at this point, a tremendous gap in our knowledge of heparin and other mucopolysaccharides exists. 

In establishing the mechanism of the biosynthesis of hyaluronate, consideration must be given to the manner of forming the d-o-glucosid-uronic acid linkage. 

Jl. Jacobson, B, and Davidson, E. A., Biosynthesis of uronic acids by skin enzymes. II. Uridine diphosphate-D-glucuronic acid-5-epimerase. J. Biol. Chem. 237, 638-642 (1962). 

In studies on the biosynthesis of cell-wall polysaccharides in cultured carrot cells, D-glucose was only incorporated into the neutral sugar residues, particularly cellulose, whereas myo-inositol appeared in the uronic acid and pentose residues. " An increase in cellulose content was observed during the thickening of the cell walls of parenchymous tissue of Discorea dumetorum tubers during storage. 

Direct oxidation of CH2OH in the presence of CH=0 is not practical, so laboratory preparations of uronic acids are limited to processes that include appropriate protection-deprotection strategies. D-Glucuronic acid, an intermediate in the biosynthesis of vitamin C and in various metabolic pathways, is biosynthesized by an enzyme-catalyzed NAD oxidation of a derivative of D-glucose. 

Most secondary monosaccharides are formed from primary sugars by the following types of reactions (for biosynthesis of some secondary monosaccharides by decarboxylation of uronic acids, see D 1.2). 

The biosynthesis of the uronic acid component of polyoxins has been studied by means of n.m.r using D-[l- C]glucose as precursor. ... 

Interest in the genetic engineering of both plants and micro-organisms for the production of tailor made amylose, amylopectin and/or starches has also been reported. Furthermore, investigations on the enzymatic modification of starch and its major components, for example the introduction of additional branches composed of glucose and/or other monosaccharides and/or uronic acids as well as amino acids or peptides, to produce carbohydrates of possibly comparable functionality to galactomannans, pectin, gum arable, etc., has been initiated. Also studies on the metabolic fate of carbohydrates in food, the biosynthesis of starch, the fine structure of starch from different sources, the effect of electrolytes on the gelatinization of starch and the development of enzymic methods for starch analyses are still active. 

The vast majority of animals and plants are able to synthesize vitamin C through a sequence of four enzyme-driven steps, which convert D-glucose to vitamin C (Fig. 12.6). In eukaryotes, vitamin C biosynthesis occurs via two highly divergent biochemical pathways. In rats and other mammals, glucose is converted into L-gulono-1,4-lactone via a complex pathway involving uronic acid derivatives and... 

EHimville, J.C. and Fry, S.C. (2000). Uronic acid-containing oligosaccharins their biosynthesis, degradation and signalling roles in non-diseased plant tissues. Plant Physiol Biochem. 38,125-140. 

Investigation of the biosynthesis of polyoxin antibiotics from labelled substrates by S. cacaoi has revealed that the 5-amino-5-deoxy-)3-D-allofuranosyl-uronic acid residue of these antibiotics is not derived via oxidation of either D-glucose or o-allose at C-6, but is formed from triose precursors. ... 

---